Mrs May, wearing black bow tie, gown and sensible black shoes, rather than the colourful kitten heels she has made her trademark, is sitting in the front row, ringed in yellow.

The formal wear was a prerequisite for the matriculation ceremony – the induction necessary for undergraduates to join the university. It would be the start of a more than 40-year journey that took her last week through the door of 10 Downing Street.

College records unearthed by The Telegraph show nine students at the all-female college studied geography, including Mrs May, in the ’74 intake.

One of them – her close friend Alicia Collinson – is an eminent barrister, married to Damian Green, whom Mrs May promoted to the Cabinet as Work and Pensions Secretary.

Another, Lady Louise Patten, is one of the most prominent women in the City, whose husband John, now Lord Patten, was once Secretary of State for Education.

Lord Patten was at the time a geography fellow at Oxford, and taught political geography to Mrs May as well as to his future wife, the then Louise Rowe. A renowned Right-winger and a devout Catholic, Lord Patten may well have been a strong influence on the impressionable teenager.

John Patten was one of our tutors. He taught us political geography. He almost certainly had an influence on Theresa.Denise Patterson, Class of '74

A third member of the geography intake was a successful literary agent who married one of the world’s best-selling novelists. Denise Patterson told The Telegraph: “John Patten was one of our tutors. He taught us political geography. He almost certainly had an influence on Theresa.

“Theresa was always interested in politics in a quiet, serious way. She wasn’t a flamboyant character but she had this burning ambition.”

Lord Patten, now aged 70, was elected as MP for Oxford in 1979 and served as a Home Office minister under Margaret Thatcher before being made education secretary under John Major in 1992.

Mrs Patterson – Denise Palmer as she then was – joined a literary agency after leaving Oxford, and in 1985 married Jack Patterson, better known under his pseudonym, Jack Higgins.

Higgins, one of the great thriller and espionage writers of all time, wrote among others The Eagle Has Landed. Last year, Mrs Patterson was appointed High Sheriff of West Sussex, during which time she acted as the Queen’s representative.

“When I was appointed High Sheriff, I wrote to Theresa because I was the Queen’s representative for the judiciary and the police, and she wrote me the most charming letter back,” said Mrs Patterson, who divides her time between West Sussex and Jersey.

Another of the class of ’74, Emma Hood, who was Emma Saunders at the time, remembers Mrs May being “always very focused on going into politics”.

Lady Hood, who is married to Sir John Hood, a former vice-chancellor of Oxford University, said: “I remember her saying, 'One day I will lead the [Conservative] Party’.”

Lady Hood, who herself enjoyed a successful career in the City, launching a financial analytics business that was ultimately bought up by Bloomberg, added: “Theresa had this steely determination to make the grade at a very senior level in politics.

“I have been blown away by what she has done, particularly when she faced down the police.”

Lady Hood, who joined the merchant bank Lazard when she left Oxford, said St Hugh’s was a “special college” in the Seventies – one of the few all-female colleges slightly out of town that gave it a fierce independence and identity.

“We were a very tight-knit group,” said Lady Hood.

Lady Patten, who married a year after leaving Oxford, began her career at Citibank and rose to become one of the most powerful women in the City.

She was appointed chairman of supermarket chain Somerfield until its takeover by the Co-op in 2009. She was also chairman of Brixton plc, then one of the UK’s biggest property firms.

Mrs May was active in both the Oxford Union and the university’s Conservative Association, and was close to Miss Collinson, who is now a family law barrister.

Damian Green was also in that circle.

Theresa Brasier left Oxford in 1977, taking a job with the Bank of England. She married Philip, who was president of the Oxford Union, in 1980.